1. Field of the Invention
The present invention relates to recombinant Trichoderma host cells producing Aspergillus fumigatus cellulolytic enzyme compositions and methods of producing and using the compositions.
2. Description of the Related Art
Cellulose is a polymer of glucose linked by beta-1,4-bonds. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the cellulose is converted to glucose, the glucose is easily fermented by yeast into ethanol.
One of the most commercially-utilized cellulolytic enzyme systems is that of Trichoderma reesei (teleomorph Hypocrea jecorina), which secretes endoglucanases that cleave cellulose chains internally, exocellobiohydrolases that degrade cellulose chains processively from the ends, releasing cellobiose, and beta-glucosidases that hydrolyze cellobiose to glucose. T. reesei as a cellulolytic enzyme production system has several advantages such as high yields of secreted proteins, productive under large-scale fermentation, a very active and well understood base cellulolytic enzyme system, and a sequenced and well annotated genome. However, disadvantages of the T. reesei cellulolytic enzyme system are that other organisms produce cellulolytic enzymes that are individually superior; hemicellulose-degrading enzymes are insufficient for hemicellulose-rich substrates, and beta-glucosidases are limiting under high solids hydrolysis.
Aspergillus fumigatus reportedly produces several cellulases (Nierman et al., 2005, Nature 438: 1151-1156). WO 2011/057140 discloses an Aspergillus fumigatus cellobiohydrolase I and gene thereof. WO 2011/057140 discloses an Aspergillus fumigatus cellobiohydrolase II and gene thereof. WO 2005/047499 discloses an Aspergillus fumigatus beta-glucosidase and gene thereof. WO 2010/138754 discloses an Aspergillus fumigatus GH61 polypeptide having cellulolytic enhancing activity and gene thereof. WO 2011/057140 discloses an Aspergillus fumigatus endoglucanase II and gene thereof. WO 2006/078256 discloses Aspergillus fumigatus GH10 xylanases. WO 2011/057140 discloses an Aspergillus fumigatus beta-xylosidase and gene thereof.
There is a need in the art for new cellulolytic enzyme systems that can be produced in commercial quantities and can deconstruct cellulosic material more efficiently.
The present invention provides recombinant Trichoderma host cells encoding Aspergillus fumigatus cellulolytic enzyme compositions and methods of producing and using the compositions.